Magnetizing System and Superconducting Magnet to Be Magnetized Therewith

ABSTRACT

A magnet magnetizing system and a superconducting magnet to be magnetized, for magnetizing a superconducting magnet to be magnetized, comprises: a magnetizing magnetic field generating means for generating and distinguishing a static magnetic field; a cooling means having an electromotive motor within the static magnetic field, which is generated from the magnetizing magnet generating means; and a bulk superconductor to be magnetized, which is thermally connected with a low-temperature portion of the cooling means, wherein the magnetizing magnetic field generating means is made up with a magnetizing superconducting bulk magnet, building other magnetizing bulk superconductor therein, the bulk superconductor to be magnetized before magnetization thereof is inserted within a space of the static magnetic field, which is generated by the magnetizing superconducting bulk magnet magnetized, and the magnetic field of the magnetizing superconducting bulk magnet is distinguished by the means for cooling the bulk superconductor inserted, down to be equal or lower than superconducting temperature, thereby magnetizing the bulk superconductor to be magnetized.

BACKGROUND OF THE INVENTION

The present invention relates to a magnetizing system and asuperconducting magnet to be magnetized therewith.

As conventional art relating to a magnet for use of magnetizing isalready known, for example, that having a bulk superconductor, as atarget to be cooled by a refrigerator, with using a coil-typesuperconducting magnet therein.

This magnet for use of magnetizing is located at a central portion ofthe superconducting magnet of the coil-type superconducting magnet, amagnetic center of which is cooled down to a very low temperature, andthis superconducting magnet is disposed within a heat insulating vacuumcontainer. In case when cooling the bulk superconductor, as the targetto be magnetizing, down to the very low temperature by the refrigerator,the bulk superconductor is disposed within the heat insulating vacuumcontainer, and an end of the bulk superconductor is thermally unified orintegrated with a cooling stage of the refrigerator for use of cooling,through a heat conductor, indirectly, and thereby building up a bulksuperconducting magnet.

The method for magnetizing comprises the following steps (1) to (4):

(1) Generating a predetermined static magnetic field by running currentfrom a magnetizing power source, after cooling the coil-typesuperconducting magnet for magnetization down to the very lowtemperature;

(2) Disposing the bulk superconductor of the bulk superconducting magnetbefore cooling at the position of the center of magnetic field within abore of the coil-type superconducting magnet for magnetization at roomtemperature. Herein, fluxes for magnetizing penetrate through within thebulk superconductor;

(3) Turning the power source of the refrigerator for the bulksuperconducting magnet “ON”, to cool the bulk superconductor down to thevery low temperature, equal or lower than a temperature for obtainingthe superconducting, and thereby brining the bulk superconductor intothe superconducting condition within the static magnetic field; and

(4) Demagnetizing the coil-type superconducting magnet formagnetization. The bulk superconductor captures the magnetic fluxespenetrating therethrough, and when completing the magnetization, itgenerates a magnetic field. The bulk superconducting magnet is taken outfrom an inside of the bore at room temperature, and thereafter therefrigerator for the bulk superconducting magnet keeps the operationthereof.

Herein, as was explained in the (3) mentioned above, there is necessityfor the refrigerator for the bulk superconducting magnet to be operatedunder the condition that the coil-type superconducting magnet formagnetization generates the magnetic field.

In general, such the refrigerator mentioned above has a compressor andan expander for compressing/expanding a helium gas therein, since itoperates under a refrigerating cycle, having processes or steps forcompressing/expanding the helium gas as a working medium thereof. Astypes of the refrigerator are a one-unit type with the compressor,directly connecting the compressor and the expander, and a split type ofconnecting both with tubes, each being separated from each other.

With the split type, since there are useless spaces within the tubes andthere is generated a pressure loss when the gas flows within the tubes,a cooling efficiency thereof is lower than that of the one-unit typewith the compressor. Because of lowering of the cooling efficiency andan increase of consumption of electric power, it is not a good policy toapply the split type from a viewpoint of energy saving. Then,explanation will be given hereinafter, on the case of applying theone-unit type with the compressor therein.

Since in a motor of the compressor are used magnetic materials, such as,magnetic steel and a permanent magnet, for example, it cannot beoperated within a space of high magnetic field. In general, it must beoperated within a space of low magnetic field, i.e., equal or lower than0.1 Tesla. On the other hand, it is necessary to generate a very highmagnetic field, such as, 5 Tesla to 10 Tesla, for magnetizing a highmagnetic field, at a central portion of the coil-type superconductingmagnet for magnetization by means of the bulk superconducting magnet.For this reason, within the space near to an end of the coil-typesuperconducting magnet, to be disposed the compressor therein, there areleakage fluxes of several Tesla, therefore it is impossible to disposethe compressor mentioned above. The space where the compressor can bedisposed, i.e., being equal or lower than 0.1 Tesla in the magneticfield, is at the position, separating by 0.4 m to 0.7 m from the end ofthe magnet. Also, since the magnet is disposed within a vacuumheat-shielding space, then the distance between the center of magneticfield of the coil-type superconducting magnet and an end of a vacuumcontainer is about 0.3 m. This is because of the following reasons.

A superconducting coil is built up through winding up a superconductivewire or cable by a large number of times, for generating the highmagnetic field, and herein, for the purpose of increasing the stabilityon cooling of the superconducting coil under a very low temperature witha thermal capacity of metal, the superconductive cable is wound around acore of a cold accumulating body, such as, of copper, by the largenumber thereof, and therefore the weight of the magnet is heavy. Aheat-shielding support body comes to be long, for supporting that weightby that heat-shielding support body within the vacuum space and forpreventing heat from invading therein from the portion of roomtemperature, and therefore the distance between the superconducting coiland the end of the container for vacuum heat-shielding becomes far fromeach other. Accordingly, the distance between the compressor portion ofthe refrigerator and the bulk superconductor is about 0.7 m when themagnetizing static magnetic field is 5 Tesla, and is about 1.0 m whenthe magnetizing static magnetic field is 10 Tesla.

[Patent Document 1] Japanese Patent Laying-Open No. Hei 10-11672 (1998).

BRIEF SUMMARY OF THE INVENTION

With the conventional art mentioned above, when trying to produce asmall-sized bulk superconducting magnet with shortening the diameter ofthe bulk superconductor, it is impossible to shorten the distancementioned above, i.e., between the compressor portion of therefrigerator and the bulk superconductor, irrespective of a diameter ofthe bulk superconductor, because the compressor must be disposed withinthe low magnetic space. Therefore, for the heat-shielding vacuumcontainer, it is necessary to build a long heat conductor therein, forthe purpose of separating the bulk superconductor and the refrigerator,and therefore a long vacuum container is needed.

Accordingly, with the magnetizing method within the conventional staticmagnetic field according to the conventional art, it is impossible toshorten the length of the bulk superconducting magnet, i.e., there is adrawback that the bulk superconducting magnet cannot be made small inthe sizes thereof.

An object, according to the present invention, is to provide amagnetizing system for a superconducting bulk magnet, thereby to achievesmall-sizing of the bulk superconducting magnet as a whole, withshortening the length of the bulk superconducting magnet, and asmall-sized bulk superconducting magnet, which is magnetized by thissystem.

For accomplishing the object mentioned above, according to the presentinvention, there is provided al. A magnet magnetizing system or asuperconducting magnet to be magnetized, for magnetizing asuperconducting magnet to be magnetized, comprising: a magnetizingmagnetic field generating means for generating and distinguishing astatic magnetic field; a cooling means having an electromotive motorwithin said static magnetic field, which is generated from saidmagnetizing magnet generating means; and a bulk superconductor to bemagnetized, which is thermally connected with a low-temperature portionof said cooling means, wherein said magnetizing magnetic fieldgenerating means is made up with a magnetizing superconducting bulkmagnet, building other magnetizing bulk superconductor therein, saidbulk superconductor to be magnetized before magnetization thereof isinserted within a space of the static magnetic field, which is generatedby said magnetizing superconducting bulk magnet magnetized, and themagnetic field of said magnetizing superconducting bulk magnet isdistinguished by said means for cooling the bulk superconductorinserted, down to be equal or lower than superconducting temperature,thereby magnetizing said bulk superconductor to be magnetized.

Also, the object mentioned above is accomplished by the magnetmagnetizing system or the superconducting magnet to be magnetized, asdescribed in the above, further comprising a temperature increasingmeans for increasing temperature of said bulk superconductor formagnetization, wherein after magnetizing said bulk superconductor to bemagnetized, which is cooled by said cooling means, the static magneticfield generated by said superconducting bulk magnet by increasingtemperature of said bulk superconductor for magnetization, within aspace of the static magnetic field generated by the bulk superconductorfor magnetization of said magnetized superconducting bulk magnet formagnetization.

Also, the object mentioned above is accomplished by the magnetmagnetizing system or the superconducting magnet to be magnetized, asdescribed in the above, wherein said magnetizing magnetic fieldgenerating means is magnetized by a coil-type superconducting magnet,which can generate and distinguish the static magnetic field, and aninduced current generation suppressing means is provided for a magnet ofsaid coil-type superconducting magnet.

Also, the object mentioned above is accomplished by the magnetmagnetizing system or the superconducting magnet to be magnetized, asdescribed in the above, wherein said induced current generationsuppressing means is built up with a heater, which is thermally unifiedwith a superconducting coil.

Also, the object mentioned above is accomplished by the magnetmagnetizing system or the superconducting magnet to be magnetized, asdescribed in the above, wherein said induced current generationsuppressing means is built up with a mechanism for switching an exitingcurrent circuit of a superconducting coil into an open circuit.

Also, the object mentioned above is accomplished by the magnetmagnetizing system or the superconducting magnet to be magnetized, asdescribed in the above, wherein said induced current generationsuppressing means is built up with a mechanism for switching an exitingcurrent circuit of a superconducting coil into a reverse induced currentsupply circuit.

7. The magnet magnetizing system, as described in the claim 1, whereinsaid magnetizing magnetic field generating means is magnetized by apulse-type normal-conducting magnet, which can generate and distinguisha changing magnetic field.

According to the present invention, it is possible to provide amagnetizing system for a superconducting bulk magnet, thereby to achievesmall-sizing of the bulk superconducting magnet as a whole, withshortening the length of the bulk superconducting magnet, and asmall-sized bulk superconducting magnet, which is magnetized by thissystem.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

Those and other objects, features and advantages of the presentinvention will become more readily apparent from the following detaileddescription when taken in conjunction with the accompanying drawingswherein:

FIG. 1 is a view for explaining a superconducting magnet for magnetizinga superconducting bulk magnet for magnetization, applying an embodimentof the present invention therein;

FIG. 2 is a view for explaining the superconducting bulk magnet formagnetization, applying the embodiment of the present invention therein;

FIG. 3 is a view for explaining the structures for magnetizing thesuperconducting bulk magnet for magnetization shown in FIG. 2 by thesuperconducting magnet shown in FIG. 1, applying the embodiment of thepresent invention therein;

FIG. 4 is a view for showing the structures of a small-sizedsuperconducting bulk magnet, applying the embodiment of the presentinvention therein;

FIG. 5 is a view for showing the structures for magnetizing thesmall-sized superconducting bulk magnet shown in FIG. 4 by thesuperconducting bulk magnet for magnetization, which is magnetized inFIG. 3, applying the embodiment of the present invention therein;

FIG. 6 is a view for showing the structures for magnetizing thesuperconducting bulk magnet shown in FIG. 2 by the superconductingmagnet, applying other embodiment of the present invention therein;

FIG. 7 is a view for showing the structures for magnetizing thesuperconducting bulk magnet shown in FIG. 2 by the superconductingmagnet, applying further other embodiment of the present inventiontherein; and

FIG. 8 is a view for showing the structures for magnetizing thesuperconducting bulk magnet shown in FIG. 2 by the superconductingmagnet, applying further other embodiment of the present inventiontherein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments according to the present invention will befully explained by referring to the attached drawings.

Embodiment 1

Hereinafter, an embodiment of the present invention will be explained byreferring to FIGS. 1 to 5 attached herewith.

FIG. 1 is a cross-section view of a superconducting magnet formagnetizing a superconducting bulk magnet for use of magnetization.

In FIG. 1, a superconducting coil 2, built up by winding asuperconductor wire or cable, such as, of NbTi, for example, around abobbin 1, made of copper, is connected with a cooling stage 4 attemperature 4K of the Gifford/McMahon type helium refrigerator 3,thermally, through a group of copper net-wires 5, being flexible, and iscooled down to the superconducting temperature of the NbTi cable orlower than that, i.e., around 4K. As a working gas of the heliumrefrigerator 3 is supplied a high pressure gas, from a compressor unit 6through a conduit 7, and a low pressure, after being expanded within therefrigerator, is collected through a conduit 8.

A periphery of the superconducting coil 2 of very low temperature issurrounded by a heat-shielding pipe or tube 9, which is cooled down totemperature, around 50K, i.e., being protected, thermally. Theheat-shielding pipe or tube 9 is thermally connected with a coolingstage 10 at temperature 50K of the helium refrigerator 3 through a groupof copper net-wires 11, being flexible, and is cooled down. Those lowtemperature constituent elements are disposed within a vacuum container12, to be shielded thermally through the vacuum, and the superconductingcoil 2, as well as, the bobbin 1, reaching to several tens Kg in theweight thereof, are supportably fixed on a wall of room temperature ofthe vacuum container 12, by means of a plural pieces of heat-shieldingsupport members 13, made of a material having small heat conductivity,such as, a plastic material, etc. An exciting current to thesuperconducting coil 2, equal to 100 A or larger than that, is suppliedfrom a current source apparatus 14, which is provided at the roomtemperature, and is collected thereto, through very thick and heavy two(2) pieces of power source cables 15. A heating current is supplied to aheater 100, which is thermally unified with the bobbing 1, from acurrent source 102 through wiring 101, thereby heating thesuperconducting coil 2 up to temperature around 10K, exceeding thesuperconducting temperature.

With supplying the exiting current to the superconducting coil 2, it ispossible to generate a predetermined high magnetic field at a center ofa bore space at room temperature at a central portion of the coil.However, because the magnetic field leaks widely, with thesuperconducting coil, if assuming that a diameter of the bore space 16at room temperature is 100 mm and the magnetic field of 10 Tesla isgenerated at the central portion thereof, for example, then the leakingmagnetic filed at a position 18 separating from an end 17 of the space16 at room temperature by 600 mm is 0.1 Tesla. In this manner, it can beseen that the leaking magnetic field generates covering over a widearea.

Next, explanation will be made on the structures of the superconductingbulk magnet 19 for use of magnetization, by referring to FIG. 2.

FIG. 2 is a view for showing the structures of the superconducting bulkmagnet 19 for use of magnetization, comprising the embodiment of thepresent invention therein.

In FIG. 2, a bulk superconductor 20 for capturing the magnetic field foruse of magnetization is formed in a cylindrical configuration, and onthe periphery thereof is unified with a protector cylinder or tube 21made of stainless or aluminum, fixing contact portions thereof eachother with an adhesive or a Wood's metal of low melting temperature, forexample. A bottom portion of the protector tube 21 is thermally unifiedwith a flange 23 of a heat conductor 22, made of copper or aluminum, forcooling, through an indium sheet or the like by means of a bolt (notshown in the figure). A flange 24 at the other end of the heat conductor22 is thermally unified with a flange 26 of cooling stage at the coolingtemperature of a small-sized helium refrigerator 25 for use of cooling,i.e., around 35K, through also an indium sheet or the like by means of abolt (not shown in the figure).

The periphery of a very low temperature portion is covered with alaminated heat-shielding member 27, and the very low temperature portionis disposed within a vacuum container 28 for the purpose of obtainingvacuum heat shielding. A vacuum container flange 29 is air-tightlyunified with a flange 30 of the small-sized helium refrigerator 25,through a vacuum ring (not shown in the figure) by means of a bolt (notshown in the figure), etc. The small-sized helium refrigerator 25 buildsin a compressor 31 for helium, i.e., the working gas therein, beingdisposed at an end thereof, and is supplied with current of severalamperes from an electric power source 32 through a power cable 33, to beoperated under low-temperature. Heat of compression, which is generatedthrough compression of the helium gas within the compressor, isdischarged into an outside of the refrigerator through a cooling jacket34, which is provided at a heat-discharge portion of the compressor. Aworking fluid of the cooling jacket 34, such as, cooling water, forexample, is collected into a cooling unit 36 through a conduit 35 madeof vinyl, and after being cooled down by a refrigerator 37 operatingwith using other coolant or a radiator of a heat exchanger between anair (not shown in the figure), etc., within a cooling unit 36, it iscompressed by a pump 38 to be sent into the cooling jacket 34, through aconduit 39 made of vinyl, for example.

Also, the bulk superconductor 20 of an amount of several Kg, which iscooled down to a very low temperature, is held to be in non-contact withthe vacuum container 28 at room temperature, i.e., it is important tokeep the thermal invasion therein not increase. In the presentembodiment, between the vacuum container 28, an outer surface of theheat conductor 22 is supported by means of rods 41, each being made of amaterial having small thermal conductivity, such as, an epoxy resin, andmovable into a radius direction of a ring 40, which is made of the epoxyresin or aluminum, through a screw, at four (4) or three (3) positionson the periphery thereof. Since a diameter of the heat conductor 22 issmaller than the diameter of the bulk superconductor 20, it is possibleto support the outer surface of the heat conductor 22, in aheat-insulating manner, on the vacuum container 28, having a temperaturedifference, with keeping a long distance therebetween, and therefore itis possible to reduce an amount of heat invasion.

An inside of the vacuum container 28 is discharged to be a vacuum, by avacuum pump 45 through a nozzle 42, a vacuum valve 43 and a conduit 44.On a side surface of the heat conductor 22 on the side of the coolingstage flange 26 of the refrigerator is attached gas absorbents 46, suchas, activated charcoal for use of gas absorption, for example, throughan adhesive or the like. After cooling the bulk superconductor 20 downto the very low temperature by the refrigerator 31, and after the gasabsorbents 46 are cooled down to be equal or lower than an absorptiontemperature, the vacuum valve 43 is closed, and therefore the conduit 44and the vacuum pump 45 can be separated from each other, to betransferred easily.

At a tip of the vacuum container 28 has a recessed space 47 of roomtemperature. Further, there are provided a heater 48, which is thermallyunified with the heat conductor 22, wiring 49 and a current source 50,to obtain such a structure for supplying heating current from thecurrent source 50, thereby heating up the bulk superconductor 20,quickly, up to temperature exceeding over the superconductingtemperature.

FIG. 3 is a view for explaining the structures for magnetizing thesuperconducting bulk magnet for use of magnetization, having theembodiment of the present invention therein.

In FIG. 3, a predetermined exciting current is supplied to thesuperconducting coil 2, which is cooled down to the very lowtemperature, from the current source apparatus 14, thereby generating apredetermined high magnetic field at a central portion of the bore space16 at room temperature, for example, a high magnetic field of 10 Teslaat the central portion of the bore space 16 at room temperature havingthe diameter of 100 mm. In this instance, the leaking magnetic field is0.1 Tesla at the position 18 separating from the end portion 17 of thespace 16 of room temperature by 600 mm. Accordingly, setting is made sothat the compressor 31 of the superconducting bulk magnet 19 for use ofmagnetization at the position 18, the bulk superconductor 20 at roomtemperature is disposed at the central portion of the bore space 16 atroom temperature. An air inside the vacuum container 28 is dischargedinto a vacuum by the vacuum pump 45, and current of several amperes issupplied from the electric power source 32 through the power cable 33,thereby to operate the refrigerator 19 under the low temperature. Atthis point, a magnetic flux of 10 Tesla within the space at roomtemperature penetrates through the bulk superconductor 20, which doesnot reach to the superconducting temperature.

After the bulk superconductor 20 is cooled down to be equal or lowerthan the superconducting temperature, and the temperature thereof is ina steady state, an induced current is generated in the bulksuperconductor 20 when reducing the current of the superconducting coil2 by sweeping the exiting current from the current source apparatus 14.This induced current continues to flow without decrease or attenuationsince the bulk superconductor 20 is in the superconducting condition,and the magnetic field is generated and the magnetic field is captured.At a time point when no current flows within the superconducting coil 2,the magnetization is completed upon the bulk superconductor 20.Thereafter, operation of the refrigerator 3 is stopped, and furtherheating current is supplied to the heater 100, which is thermallyunified with the bobbin 1, through the wiring 101, thereby heating thesuperconducting coil 2 up to temperature exceeding the superconductingtemperature of the superconducting coil 2, i.e., around 10K.

In this condition, the superconducting bulk magnet 19 for use ofmagnetization is pull out from the space 16 at room temperature. In thistime, since in the superconducting coil 2 is generated the inducedcurrent, for building up a magnetic field in such a direction to trapthis magnetic field in the space 16 at room temperature, due to themagnetic field generated by the bulk superconductor 20, then such asuction force is generated on the superconducting bulk magnet 19 for useof magnetization, as to bring hard to be pulled out, and a tension forceis generated on the helium refrigerator 25. However, since thesuperconducting coil 2 is heated and therefore not in thesuperconducting state, then the induced current generated distinguishesthrough Joule heat, and therefore a resistance against the pulling-outcomes to be small, i.e., the bulk magnet can be pulled out from thespace 16 at room temperature, easily, within a short time period.

FIG. 4 is a view for explaining the structures the small-sizedsuperconducting bulk magnet, having the embodiment of the presentinvention therein.

In FIG. 4, a small-sized superconducting bulk magnet 51 for capturingthe magnetic field is formed into a column-like shape, and the peripherythereof is in a protecting tubular body 52 of stainless steel oraluminum, fixing the portion contacting with each other by an adhesiveor Wood's metal having low melting temperature, and they are alsothermally unified with each other. A bottom portion of the protectingtubular body 52 is thermally unified with a cooling stage flange 54 of asmall-sized helium refrigerator 53 for cooling down to coolingtemperature around 40K, by means of a bolt (not shown in the figure),through an indium sheet or the like, for the purpose of cooling thereof.

The periphery of the very low temperature portion is covered with alaminated heat-shielding member 54. Also, the very low temperatureportion is disposed within a vacuum container 55 for vacuum shieldingthereof. A vacuum container flange 56 is air-tightly unified with aflange 57 of the small-sized helium refrigerator 53, by means of a bolt(not shown in the figure), or the like, through a vacuum ring (not shownin the figure), for example. The small-sized helium refrigerator 53builds in a compressor 58 for helium, i.e., the working gas therein,being disposed at an end thereof, and is supplied with current ofseveral amperes from an electric power source 59 through a power cable60, to be operated under low-temperature. Heat of compression, which isgenerated through compression of the helium gas within the compressor58, is discharged into an outside of the refrigerator through a coolingjacket 61, which is provided at a heat-discharge portion of thecompressor 58. A working fluid of the cooling jacket 61, such as,cooling water, for example, is collected into a cooling unit 63 througha conduit 62 made of vinyl, and after being cooled down by arefrigerator 64 operating with using other coolant or a radiator of aheat exchanger between an air (not shown in the figure), etc., within acooling unit 63, it is compressed by a pump 65 to be sent into thecooling jacket 61, through a conduit 66 made of vinyl, for example.

An inside of the vacuum container 55 is discharged to be a vacuum, by avacuum pump 70 through a nozzle 67, a vacuum valve 68 and a conduit 69.In the vicinity of the cooling stage flange 54 of the refrigerator isattached gas absorbents 71, such as, activated charcoal for use of gasabsorption, for example, through an adhesive or the like. After coolingthe small-sized bulk superconducting magnet 51 down to the very lowtemperature by the refrigerator 53, and after the gas absorbents 71 arecooled down to be equal or lower than an absorption temperature, thevacuum valve 68 is closed, and therefore the conduit 69 and the vacuumpump 70 can be separated from each other, to be transferred easily.

FIG. 5 is a view for explaining the structures for magnetizing thesmall-sized superconducting bulk magnet by the superconducting bulkmagnet for use of magnetization.

In FIG. 5, within the superconducting bulk magnet 19, which ismagnetized with the method explained in FIG. 3, the magnetic fluxescaptured by the magnetized bulk superconductor 20 build up a strongmagnetic field of about 7 Tesla, within the space 47 at roomtemperature. However, the a space of leaking magnetic field is narrow,i.e., a position 72 separating from an end surface 71 of the magnet byaround 60 mm is a boundary of the leaking magnet field of 0.1 Tesla.Accordingly, setting is made so that the small-sized superconductingbulk magnet 51 at room temperature is disposed within the space at roomtemperature 47 while disposing the compressor 58 for the small-sizedsuperconducting bulk magnet 51 within a space of the magnetic fieldequal or lower than 0.1 Tesla. Discharging an air within the vacuumcontainer 55 (shown in FIG. 4) by the vacuum pump 70 with opening thevacuum valve 68, and current of several amperes is supplied from theelectric power source 59 through the power cable 60, thereby to operatethe refrigerator 53 (shown in FIG. 4) under low temperature. At thispoint, a magnetic flux of 7 Tesla within the space at room temperaturepenetrates through the small-sized superconducting bulk magnet 51, whichdoes not reach to the superconducting temperature.

After the small-sized superconducting bulk magnet 51 is cooled down tobe equal or lower than the superconducting temperature and thetemperature thereof is in a steady state, the refrigerating operation ofthe helium refrigerator 25 for the superconducting bulk magnet 19 formagnetization, a heating current is supplied from the current source 50so as to heat up the heater 48, and thereby heating the bulksuperconductor 20 up to the temperature higher than the superconductingtemperature 100K. When the bulk superconductor 20 is heated to be higherthan 100K of the temperature thereof, the magnetic fluxes captured bythe bulk superconductor 20 distinguish. When the magnetic field withinthe space 47 at room temperature is reduced, an induced current isproduced in the small-sized superconducting bulk magnet 51, and thatinduced current can continue to flow without decrease or attenuationsince the small-sized superconducting bulk magnet 51 is in thesuperconducting condition, and the magnetic field is generated and themagnetic field is captured. At a time point when no current flows in thebulk superconductor 20, the magnetization is completed upon thesmall-sized superconducting bulk magnet 51.

In this condition, a small-sized superconducting bulk magnet 80 is pullout from the space 47 at room temperature of the superconducting bulkmagnet 19 for magnetization. In this time, since the bulk superconductor20 is an insulating body since it is not in the superconducting state,no induced current is generated, and therefore it can be pulled out fromthe space 47 at room temperature, easily.

Doing in this manner, the small-sized superconducting bulk magnet 51 ofthe small-sized superconducting bulk magnet 80 can capture the magneticfield of about 6 Tesla. Accordingly, there is no necessity of a membercorresponding to the long heat conductor 22, which was necessary fordisposing the compressor for the refrigerator outside the field ofleaking magnetic field of 0.1 Tesla, as is in the case of thesuperconducting bulk magnet 19 for magnetization, then it is possible toshorten the length of the main body of the superconducting magnet of arefrigerator-cooling type. Therefore, there can be obtained an effectfor enabling to generate a strong magnetic field on a surface by amagnet of lightweight and low-cost.

In this manner, with the present embodiment, since there can be providedthe superconducting bulk magnet for magnetization, which was magnetizedby a coli-type magnet in advance, as a magnetization magnet fornarrowing a region of the leaking magnetic field in an outside of themagnet, within the magnetization operating method for thesuperconducting bulk magnet, it is possible to shorten the length of themagnet including the refrigerator for the other refrigerator coolingtype superconducting bulk magnet to be magnetized; there can be achievedan effect of obtaining small-sizing and light-weighting of therefrigerator-cooling type superconducting bulk magnet.

Also, with the present embodiment, since the surface area thereof can bereduced by shortening the length of the low-temperature portion of therefrigerator-cooling type superconducting bulk magnet, then it ispossible to reduce an amount of thermal invasion from the portion atroom temperature, and for this reason, a cooling capacity can be madesmall, of the refrigerator to be unified for cooling down to apredetermined temperature. With this, it is possible to reduce the costof the refrigerator and the cost of the refrigerator-cooling typesuperconducting bulk magnet.

Embodiment 2

FIG. 6 is a view for explaining the structures for magnetizing thesuperconducting bulk magnet for magnetization, which has a secondembodiment therein.

In FIG. 6, an aspect of the present embodiment differing from that shownin FIG. 3 lies in that, after the bulk superconductor 20 is cooled downto be equal or lower than the superconducting temperature, and thetemperature is in the steady state thereof, an induced current isgenerated in the bulk superconductor 20 when reducing the current of thesuperconducting coil 2 by sweeping the exiting current from the currentsource apparatus 72. This induced current continues to flow withoutdecrease or attenuation because the bulk superconductor 20 is in thesuperconducting condition, and the magnetic field is generated and themagnetic field is captured. At a time point when no current flows withinthe superconducting coil 2, the magnetization is completed upon the bulksuperconductor 20. Thereafter, operation of the refrigerator 3 isstopped.

Herein, within the exiting current circuit of the current sourceapparatus 72 is made up a circuit for building up an open circuit (notshown in the figure), and there is also provided an exchange switch (notshown in the figure) for switching to that open circuit. After stoppingthe operation of the refrigerator 3, the exiting current circuit isswitched into the open circuit. In this condition, the superconductingbulk magnet 19 for magnetization is pulled out from the space 16 at roomtemperature. In this instance, due to the magnetic field generated bythe bulk superconductor 20, an induced current tries to generate in thesuperconducting coil 2, for building up the magnetic field in adirecting of closing this magnetic field within the space 16 at roomtemperature. However, with switching the exiting current circuit intothe open circuit, no induced current flow therein, and there can beobtain an effect that the resistance against pulling-out come to besmall, and that the bulk magnet can be pulled out from the space 16 atroom temperature, easily.

Embodiment 3

FIG. 7 is a view for explaining the structures for magnetizing thesuperconducting bulk magnet for magnetization, which has an embodiment 3therein.

In FIG. 7, an aspect of the present embodiment differing from that shownin FIG. 6 lies in that, after the bulk superconductor 20 is cooled downto be equal or lower than the superconducting temperature, and thetemperature is in the steady state thereof, an induced current isgenerated in the bulk superconductor 20 when reducing the current of thesuperconducting coil 2 by sweeping the exiting current from the currentsource apparatus 73. This induced current continues to flow withoutdecrease or attenuation because the bulk superconductor 20 is in thesuperconducting condition, and the magnetic field is generated and themagnetic field is captured. At a time point when no current flows withinthe superconducting coil 2, the magnetization is completed upon the bulksuperconductor 20. Thereafter, operation of the refrigerator 3 isstopped. Herein, within the exiting current circuit of the currentsource apparatus 73 is made up a circuit for building up an reverseinduced current circuit (not shown in the figure) for flowing current ina direction reversing to the induced current to be generated, and thereis also provided an exchange switch (not shown in the figure) forswitching to that circuit. After stopping the operation of therefrigerator 3, the exiting current circuit is switched into the reverseinduced current circuit. In this condition, the superconducting bulkmagnet 19 for magnetization is pulled out from the space 16 at roomtemperature. In this instance, since a magnetic force is built up on thesuperconducting coil 2, in a direction of pushing out the bulksuperconductor 20 magnetized, it can be pulled out easily, and there canbe obtained an effect that it can be pulled out from the space 16 atroom temperature within a shot time-period.

Embodiment 4

FIG. 8 is a view for explaining the structures for magnetizing thesuperconducting bulk magnet for magnetization, which has an embodiment 4therein.

In FIG. 8, an aspect of the present embodiment differing from that shownin FIG. 3 lies in that, after the bulk superconductor 20 is cooled downto be equal or lower than the superconducting temperature, from the bulksuperconductor 20 cooled down to the temperature of liquid nitrogen to anormal-conducting coil 74, a pulse-like current is supplied from a pulsecurrent source 76 through wiring 75, i.e., there is disclosed theconstruction of the magnetizing method for magnetizing the bulksuperconductor 20, in accordance with the method for compulsivelyentering magnetic fluxes, in a pulse-like manner, into the bulksuperconductor 20 in the superconducting state.

With the present embodiment, though the magnetic field is small, whichcan be magnetized on the bulk superconductor 20, but the coil formagnetization can be built up with a normal-conducting magnet, and therecan be obtained an effect of reducing the costs of the constituent partsthereof.

In this manner, with the present embodiment, since the superconductingbulk magnet for magnetization, which was magnetized by the coil-typemagnet in advance, is provided as the magnet for magnetization, so as tonarrow the region of the leaking magnetic field in the outside of themagnet, within the magnetizing operating method for the superconductingbulk magnet, it is possible to provide a magnet for narrowing the regionof the leaking magnetic field, and with this, there can be obtained aneffect that the magnetization can be achieved upon the superconductingbulk magnet being short in the length of the magnet, including therefrigerator for the other refrigerator cooling type superconductingbulk magnet to be magnetized, and with this magnetization operatingmethod, there can be obtained also an effect of providing a small-sizedrefrigerator-cooling type superconducting bulk magnet, which is short inthe length and light in the weight thereof.

As was mentioned above, with the present invention, since the leakingmagnetic field is small when using the superconducting bulk magnet formagnetization therein, then it is not necessary to provide the membercorresponding to the long heat conductor 22, which is necessary fordisposing the compressor of the refrigerator for the superconductingbulk magnet to be magnetized within an outside of the magnetic fieldwhere the leaking magnetic field is 0.1 Tesla, and therefore it ispossible to shorten the length of the superconducting bulk magnet to bemagnetized, as a whole, and for this reason, there can be obtained aneffect of enabling to generate a strong magnetic field on the surfacethereof, by a magnet, being lighter in the weight and with a low cost.

While we have shown and described several embodiments in accordance withour invention, it should be understood that disclosed embodiments aresusceptible of changes and modifications without departing from thescope of the invention. Therefore, we do not intend to be bound by thedetails shown and described herein but intend to cover all such changesand modifications that fall within the ambit of the appended claims.

1. A magnet magnetizing system, for magnetizing a superconducting magnetto be magnetized, comprising: a magnetizing magnetic field generatingmeans for generating and distinguishing a static magnetic field; acooling means having an electromotive motor within said static magneticfield, which is generated from said magnetizing magnet generating means;and a bulk superconductor to be magnetized, which is thermally connectedwith a low-temperature portion of said cooling means, wherein saidmagnetizing magnetic field generating means is made up with amagnetizing superconducting bulk magnet, building other magnetizing bulksuperconductor therein, said bulk superconductor to be magnetized beforemagnetization thereof is inserted within a space of the static magneticfield, which is generated by said magnetizing superconducting bulkmagnet magnetized, and the magnetic field of said magnetizingsuperconducting bulk magnet is distinguished by said means for coolingthe bulk superconductor inserted, down to be equal or lower thansuperconducting temperature, thereby magnetizing said bulksuperconductor to be magnetized.
 2. The magnet magnetizing system, asdescribed in the claim 1, further comprising a temperature increasingmeans for increasing temperature of said bulk superconductor formagnetization, wherein after magnetizing said bulk superconductor to bemagnetized, which is cooled by said cooling means, the static magneticfield generated by said superconducting bulk magnet by increasingtemperature of said bulk superconductor for magnetization, within aspace of the static magnetic field generated by the bulk superconductorfor magnetization of said magnetized superconducting bulk magnet formagnetization.
 3. The magnet magnetizing system, as described in theclaim 1, wherein said magnetizing magnetic field generating means ismagnetized by a coil-type superconducting magnet, which can generate anddistinguish the static magnetic field, and an induced current generationsuppressing means is provided for a magnet of said coil-typesuperconducting magnet.
 4. The magnet magnetizing system, as describedin the claim 3, wherein said induced current generation suppressingmeans is built up with a heater, which is thermally unified with asuperconducting coil.
 5. The magnet magnetizing system, as described inthe claim 3, wherein said induced current generation suppressing meansis built up with a mechanism for switching an exiting current circuit ofa superconducting coil into an open circuit.
 6. The magnet magnetizingsystem, as described in the claim 3, wherein said induced currentgeneration suppressing means is built up with a mechanism for switchingan exiting current circuit of a superconducting coil into a reverseinduced current supply circuit.
 7. The magnet magnetizing system, asdescribed in the claim 1, wherein said magnetizing magnetic fieldgenerating means is magnetized by a pulse-type normal-conducting magnet,which can generate and distinguish a changing magnetic field.
 8. Asuperconducting magnet to be magnetized, comprising: a magnetizingmagnetic field generating means for generating and distinguishing astatic magnetic field; a cooling means having an electromotive motorwithin said static magnetic field, which is generated from saidmagnetizing magnet generating means; and a bulk superconductor to bemagnetized, which is thermally connected with a low-temperature portionof said cooling means, wherein said magnetizing magnetic fieldgenerating means is made up with a magnetizing superconducting bulkmagnet, building other magnetizing bulk superconductor therein, saidbulk superconductor to be magnetized before magnetization thereof isinserted within a space of the static magnetic field, which is generatedby said magnetizing superconducting bulk magnet magnetized, and themagnetic field of said magnetizing superconducting bulk magnet isdistinguished by said means for cooling the bulk superconductorinserted, down to be equal or lower than superconducting temperature,thereby magnetizing said bulk superconductor to be magnetized.
 9. Thesuperconducting magnet to be magnetized, as described in the claim 8,further comprising a temperature increasing means for increasingtemperature of said bulk superconductor for magnetization, wherein aftermagnetizing said bulk superconductor to be magnetized, which is cooledby said cooling means, the static magnetic field generated by saidsuperconducting bulk magnet by increasing temperature of said bulksuperconductor for magnetization, within a space of the static magneticfield generated by the bulk superconductor for magnetization of saidmagnetized superconducting bulk magnet for magnetization.
 10. Thesuperconducting magnet to be magnetized, as described in the claim 8,wherein said magnetizing magnetic field generating means is magnetizedby a coil-type superconducting magnet, which can generate anddistinguish the static magnetic field, and an induced current generationsuppressing means is provided for a magnet of said coil-typesuperconducting magnet.
 11. The superconducting magnet to be magnetized,as described in the claim 10, wherein said induced current generationsuppressing means is built up with a heater, which is thermally unifiedwith a superconducting coil.
 12. The superconducting magnet to bemagnetized, as described in the claim 10, wherein said induced currentgeneration suppressing means is built up with a mechanism for switchingan exiting current circuit of a superconducting coil into an opencircuit.
 13. The superconducting magnet to be magnetized, as describedin the claim 10, wherein said induced current generation suppressingmeans is built up with a mechanism for switching an exiting currentcircuit of a superconducting coil into a reverse induced current supplycircuit.
 14. The superconducting magnet to be magnetized, as describedin the claim 8, wherein said magnetizing magnetic field generating meansis magnetized by a pulse-type normal-conducting magnet, which cangenerate and distinguish a changing magnetic field.